opponents of the "bono act" consider the legislation to be corporate welfare and have tried (but failed) to have it declared unconstitutional, claiming that such an act is not "necessary and proper" to accomplishing the constitution's stated purpose of "promot[ing] the progress of science and useful arts". they argue that most works bring most of the profits during the first few years and are pushed off the market by the publishers thereafter. thus there is little economic incentive in extending the terms of copyrights except for the few owners of franchises that are wildly successful, such as disney. they also point out that the tenth amendment can be construed as placing limits on the powers that congress can gain from a treaty. more directly, they see two successive terms of approximately 20 years each (the copyright act of 1976 and the bono act) as the beginning of a "slippery slope" toward a perpetual copyright term that nullifies the intended effect and violates the spirit of the "for limited times" language of the united states constitution, article i, section 8, clause 8.