Final answer:
The First Amendment, which includes the right to petition the government, best protects the activities of lobbyists. This aspect of freedom of speech and assembly is essential to the practice of lobbying and is at the core of the democratic process.
Step-by-step explanation:
The constitutional right and rule that best protects the activities of lobbyists is stated in the First Amendment, specifically the provision that protects 'the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.'
This is directly applicable to the practice of lobbying, where individuals, groups, or organizations attempt to influence legislation or policy through communication with government officials. The ability to petition is a form of freedom of speech and assembly, and is the foundational right under which lobbying activities are protected.
The process of lobbying is an essential part of the democratic process, as it allows for various interest groups to express their views and attempt to sway legislators and policy makers. While the extent of protection for certain lobbying activities can be a subject of debate, the First Amendment ensures that the core function of lobbying as a petition to the government is constitutionally safeguarded.