Liz Buchanan BVSc MRCVS
Hello - in the eyes of the law (we are based in the UK) animals are property. It wouldn't be okay to abduct someone else's pet to take it to the vets. There might be some reasonable flexibity around this in the case of an acute emergency eg you being first at the scene of a car accident, but the vets would still have to scan the cats' ID chip and call the owner for permission to treat as soon as they reasonably could eg having put a patient that can't breathe into an oxygen tent and before doing any investigations or giving drugs, for example. If you feel as though the cat is unlikely to survive / cope overnight, you could seek the advice of the RSPCA, who may have a local emergency line / Inspectors and offer advice. However, just because the cat comes to your house a lot, doesn't give you any right to make decisions on the owners' behalf; nor does it necessary mean that it is being treated badly at home. Some cats are intrinsically skinny and 'hungry,' because of hyperthyroidism or cancer, for example, rather than neglect. We would therefore reccommend extreme caution and asking the owners' advice / permission before interfering.