How have courts interpreted the "imposed by law" exception to the constitutional debt limit?

However, this argument assumes the law must not only impose a duty to incur an expenditure but must also set the exact amount of that expenditure. Although this construction finds some support in certain language in Lewis v. Widber, supra, subsequent cases have removed this restriction on the "imposed by law" exception to the constitutional debt limit. (See cases discussed at pages 236-237, ante.)