From Longman Dictionary of Contemporary Englishbe (a) party to somethingbe (a) party to somethingformalTAKE PART/BE INVOLVED to be involved in an activity or decision I was not a party to this discussion. → party
Examples from the Corpus
be (a) party to something• The second mortgagee should also be a party to receive the additional covenant of the wife.• Left-wing factors are a party to this move.• Others who spoke to Mr Ayob hoped they might be party to something big.• It occurred to Alexei to wonder how many people were party to the arrangement.• Such States are parties to the treaty, but not to the proceedings.• I won't be party to your bitching yourself on the sly.• Whatever was happening in there they were certainly not going to be a party to it.• I refuse to be a party to anything so dishonest.• In practice, therefore, where a mortgage affects the property the mortgagee will be a party to the conveyance or transfer. 