Relationships with Interest Groups - AP US Government

Controversy has arisen in the past few decades over the role of former members of Congress in lobbying. This has led to what is called a "revolving door" in Congress. In light of this, light restrictions have been added that prevent former members of Congress from lobbying to former staff for one year, and other members of Congress for two. Students should be aware of current controversies surrounding interest groups in the United States.

With respect to the other answers, few states have restrictions on state funds being used to lobby, lobbyists must register but do not need to apply for licensing, lobbyists can certainly work in multiple states, and foreign entities can lobby the government as long as they adhere to certain restrictions.