Final answer:
The Bill of Rights was applied to tribal governments largely through the Indian Civil Rights Act of 1968, among other legal developments, with its incorporation into federal law ensuring that many, but not all, rights were guaranteed to Native American tribes.
Step-by-step explanation:
Most of the provisions in the Bill of Rights were applied to tribal governments through the process of selective incorporation, which started more broadly with states in the 20th century. Although not originally applying to the states, or by extension to tribal governments, the Supreme Court began a process of selective incorporation beginning in 1897, determined by whether state laws violated principles of liberty and justice deemed fundamental to the inalienable rights of a citizen.
This process was extended, in part, to tribal governments with the passing of the Indian Civil Rights Act of 1968, which guaranteed Indian tribes most of the rights of the United States Bill of Rights. The Indian Self-Determination Act of 1975 and the Education Assistance Act gave tribal governments more autonomy. Despite these advances, Native American civil rights issues, including tribal autonomy and self-government, persist today.