The National Assn. of Broadcasters has joined with other trade organizations in challenging a new law that limits the deductibility of lobbying as a business expense.The law, which took effect Jan. 1, requires either that trade associations pay a special “proxy tax” on coin spent for lobbying, or that a trade org inform its members that a portion of their dues are no longer tax-deductible. The law also requires trade groups to pay taxes for monitoring and research that may be used in lobbying. Lobbyist protests The American Society of Association Executives — a lobbying organization for lobbyists — filed suit this week to block the new law. Ten other groups, including the NAB, joined in the action. NAB general counsel Jeff Baumann said the provision of the new law requiring new taxes for monitoring and researching issues creates “a serious disincentive” against the NAB using its employees to assist federal and state lawmakers in research gathering. Baumann also expressed fear that smaller radio and TV stations might drop their NAB membership if they’re no longer permitted to deduct part of their annual dues for lobbying.