Any Willing Provider Glossary Home Legislation compelling insurers to sign a participation agreement with any provider (such as a pharmacy or physician) that agrees to abide by the same terms of the contract and to accept the same payment level as other providers. An underlying purpose of the law is to preserve the patient’s freedom of choice. This regulation directly impacts hmos and preferred provider organizations, which attempt to control health care costs, and quality by selectively contracting with providers, monitoring their performance, and rewarding the most efficient providers.