https://www.techdirt.com/articles/20200215/19521643925/cbp-memo-confirms-bus-drivers-have-right-to-deny-agents-permission-to-search-buses-passengers.shtml

Customs and Border Protection has confirmed that its agents can't legally do one of things they've been doing pretty regularly. Under Trump, the CBP has stepped up its sweeps of mass transportation, targeting buses operated by Greyhound and others.

These searches are happening as far inland as the law allows, up to 100 miles from any border (and, technically, any international airport). This isn't just happening near the southern border. Travelers in New York and Maine have reported being questioned and otherwise harassed by CBP agents, who have been given permission to search buses by drivers.