Final answer:
The US Coast Guard can board vessels under various conditions, including enforcement of ballast water regulations, prevention of piracy under Section 8 Clause 10 of the US Constitution, and for safety and security inspections, among other reasons.
Step-by-step explanation:
The US Coast Guard is authorized to board vessels under a variety of circumstances, as outlined across different statutes and regulations. While there is no specific "Termination of Use Act" mentioned in the provided information, the Coast Guard does have broad powers of enforcement. One such regulation pertains to ballast water (BW) management. Under the National Invasive Species Act of 1996, vessels operating in US waters and capable of carrying BW must submit a Ballast Water Report (BWR).
In terms of security and defense against piracy, Section 8 Clause 10 of the US Constitution empowers Congress to punish piracy, which has implications for the authority of the Coast Guard in protecting US shipping, including boarding vessels when piracy is suspected. Additionally, all commercial ships are subject to regulation in terms of tonnage duties as Congress has the authority over these (although they should not do so without Congressional consent in time of peace).
However, there are numerous conditions under which the US Coast Guard may exercise their power to board a vessel, including but not limited to: suspicion of violation of maritime laws, enforcement of immigration and customs regulations, safety inspections, and security concerns. The actual conditions will depend on the specific legal context and purpose of the boarding.