Mae porfelaeth yn gysyniad cyfraith gwlad; nid oes unrhyw gyfraith statud berthnasol. Mae cyfraith porfelaeth yn hollol ddomestig (er bod cysyniad tebyg yn hysbys yng nghyfraith yr UE).
Mae'r gyfraith fel y nodwyd yn yr erthygl hon yn gywir ar gyfer Cymru, Lloegr, yr Alban a Gogledd Iwerddon.
Trosolwg o’r Pwnc
1. Mae porfelaeth yn drefniant cytundebol a thrwyddi caniateir i berchennog anifail (y "porwr") ei gadw ar dir sy'n perthyn i rywun arall (y "porfelwr"), at ddibenion pori. Bydd perchennog yr anifail fel arfer yn talu'r porfelwr swm rheolaidd o dan y contract.
2. Hanfod porfelaeth yw ei fod yn ôl y gyfraith ond yn rhoi hawl i’r porwr bori heb fod y tir yn ei feddiant (heb fod ganddo chwaith denantiaeth neu fudd arall yn y tir). Mae'r trefniant wedi ei ddadansoddi fel elw à prendre lle nad oes gofyn iddo, yn wahanol i'r rheol arferol, gael ei greu trwy weithred. Mae'r trefniant hefyd yn debyg i drwydded gytundebol mewn perthynas â'r tir.
3. " The features of an agistment agreement are well known. The essentials are first that the animals to be agisted are the property of the person delivering them to the farmer, and they remain that person's property. The farmer's obligation is to feed the animals and deliver up those animals to the owner on demand, but the animals are not at his risk. He is only liable for injury arising from negligence or neglect of reasonable and proper care of the animals. All the farmer gets out of the agreement is the agreed remuneration for feeding the animals. "
Capon, Re  Ch. 442.
4. " Labelling an arrangement as an agistment will not make it one if its true substance is that of a sale subject to conditions or some other kind of arrangement "
Capon, Re  Ch. 442.
5. " Agistment arrangements do not give the agister a lien over the animals to enforce payment under the contract "
Southern Livestock Producers, Re  1 W.L.R. 24.
6. Mae'r porfelwr yn gyfrifol, yn amodol ar gyfyngiadau a drafodwyd yn yr awdurdodau, am les yr anifeiliaid ac am eu cadw'n ddiogel, gyda golwg ar eu dychwelyd mewn cyflwr da ar alw.
7. " The law of England regarding agistment is the same. The English law is "if a man takes in a horse or other cattle to graze and depasture in his grounds, which the law calls agistment, he takes them upon an implied contract to return them on demand to the owner" (Blackstone, Commentaries, Book II. p.404). "
Hutchinson v MacInnes 1947 S.L.T. (Sh. Ct.) 51.
8. " ...at common law the agister takes none of those risks, but is only liable for negligence. "
Capon, Re  Ch. 442.
Porfelaeth o wahaniaethu rhyngddi a threfniadau eraill
9. " The sale or lease of the grass keep on pasture land for a definite period is not to be confounded with agistment or "tacking" as it is locally termed. The latter consists of the taking in by the farmer of another man's sheep or cattle (usually at so much per head per week) without binding himself to depasture them on any particular part of the farm, whereas the former consists of a grant for a definite period (usually in consideration of a lump sum) of the growing grass crop on a specified field or fields. "
Richards v Davies  1 Ch. 90.
Rhesymau dros fynd i mewn i borfelaeth
10. " Such arrangements can occur where an active farmer has some surplus land from which he wishes to derive an additional income. They commonly occur where an elderly farmer who no longer wishes to actively farm wants to earn an income from his land without losing control of his property. "
McCall v Revenue and Customs Commissioners  NICA 12.
11. Efallai y bydd bodolaeth trefniadau porfelaeth o bwys wrth benderfynu ar natur sefydliad amaethyddol, ac a oes gostyngiadau ar gael, at ddibenion treth: gweler: McCall v Revenue and Customs Commissioners  NICA 12 ac erthyglau mewn cyfnodolion a ysgrifennwyd ers y penderfyniad:
a. Business property relief: evolving case law and practice for landed estates P.C.B. 2010, 6, 328-335;
b. Taking stock: future approaches to grazing arrangements P.C.B. 2009, 6, 381-388;
c. McCall and Another (Personal Representatives of McClean Deceased) v Revenue and Customs Commissioners: no BPR on land subject to Northern Ireland grazing agreement (Case Comment) P.C.B. 2009;
d. Taxpayer loses McClean appeal - what are the implications for conacre and agistment lettings? Writ 2009, 199 (Sep), 22-25;
e. When will farming activities attract business property relief? (Case Comment) P.C.B. 2008, 5, 272-279.
12. Bydd gan y porfelwr rywfaint o gyfrifoldeb am yr anifeiliaid mewn perthynas â thrydydd partïon, ond mae'r cyfrifoldeb yn disgyn yn bell o unrhyw beth tebyg i atebolrwydd llwyr am unrhyw ddifrod a achosir.
13. " One error which plainly runs through the judge's observations is the repeated reference to malice. One thing that is clear in this case is that the filly had no malice whatever. But, apart from this, in my opinion the judge puts too high a standard of care upon the defendants when he required them to guard against the chance of a purely accidental and unpremeditated injury from young horses loose in a field. To impose such a duty, in my opinion, is quite unreasonable, and goes far beyond anything established by legal authority. It might well render agistment of animals impossible wherever a field abuts on an unfenced highway. "
Fitzgerald v Cooke (ED and AD) Bourne (Farms)  1 Q.B. 249.
14. Cymru a Lloegr, yr Alban a Gogledd Iwerddon: Ymddengys fod sylwedd cyfraith porfelaeth yn fras yr un fath ym mhob un o’r tair awdurdodaeth yn y DU, er gwaethaf rhai newidiadau o ran terminoleg ac arfer lleol, ac mae'n ymddangos bod y llysoedd yn cymhwyso awdurdodau rhwng y tair awdurdodaeth. Gweler, er enghraifft: Hutchinson v MacInnes 1947 S.L.T. (Sh. Ct.) 51; McCall v Revenue and Customs Commissioners  NICA 12.
Yr Undeb Ewropeaidd
15. Mae porfelaeth yn derm a geir mewn deddfwriaeth yn yr UE ac mewn achosion a benderfynwyd, sy’n cael ei ddefnyddio fwy neu lai yn yr un modd ag yng nghyfraith gwlad y DU. Gweler, er enghraifft, Rheoliad 868/2008 ar y ffurflen i ffermydd i’w defnyddio i bennu incwm o daliadau amaethyddol a dadansoddi gweithrediad busnes daliadau o’r fath.
Contractau gaeafu modern
16. " We have come to the view that Mr Kermack was right to say that a modern wintering contract has elements which can be seen as additions to the basic concept discussed by Bell. If there was a dispute about an admitted contract of agistment, evidence of current practice might well show how the implications of the contract had grown over the years. Such considerations would not address the question of whether any particular arrangement was agistment or not. Whatever might fall to be implied in the case of any specific contract in modern circumstances we accept that the contract of custody of sheep, known to Bell as depasturage, would have involved only a duty to provide adequate grass and take care for the safety of the stock. ... In short, we are satisfied that the fact that the applicant might never have considered whether the sheep needed extra care or treatment, or provided food for them when they could not get at the grass, would not by itself demonstrate that the arrangement was not one of agistment. The fact that the respondents might have provided extra feeding for the stock would not be critical if there was enough grass there in any event to keep the animals in reasonable health. There might be inferences to be drawn from an arrangement which left all responsibility for stock to the stock-owner but this would simply be a factor to weigh against other matters in considering whether the underlying arrangement was properly described as agistment or let. ... We determine that a contract of care and custody of sheep, of the type referred to as "agistment", does not necessarily involve the custodier in provision of feeding other than by reference to there being adequate pasture to maintain the agisted stock in a reasonable state of health. "
John Pollock and Sons Ltd v Robert Rennie (A Firm) 2014 G.W.D. 19-358