If you define membership in the Party, as the government, did that one must be paying dues, perhaps have a signed card somewhere, and more importantly be under Party discipline then Harry Bridges was not a member of the Party. He always said that 95% of the accusations against him were true, but not the final 5%, which was Party membership. The worst that could be said was that he may not have been as forthcoming about how close he was to the Party, while not actually being a member, although 95% covers an awful lot of ground. Bridges was always his own man, bucked the Party line on numerous occasions, particularly in '34, when he organized his longshoremen into the ILA when the Party was demanding dual unionism, in '37 when he led them again out of the AFL and into the CIO, abandoning the ILA and forming an independent union, this at a time when the Party had changed its demands from dual unionism to boring within. Again in 1960 with the M & M agreement Harry brought containerization and modernization to the west coast docks, dragging the reluctant shippers along with him. For this Harry was denounced by the Party as a "class collaborator."
Harry was first prosecuted by the government under a membership clause. When they could not prove he was a member, they changed the law to "affiliation" and convicted him on that. The Supreme Court threw all of it out twice as absurdly vague and unconstitutional under either "membership" or "affiliation."