To know where to find relevant government information, it's important to know which level and branch of government influences a topic. Is the issue federal, state, or local? How do the legislative, judicial, and executive branches of that level impact it? Which level and branch of government you need to work with will vary based on your advocacy goals, and each of those government entities will produce unique documents that are found in different places.
Congress writes legislation (bills) and votes on whether those bills become law. Bills often go through many revisions in both the House of Representatives and the Senate before reaching the form that is passed and becomes legally binding. Congress may solicit testimony from experts and members of groups who might be impacted by a law during the drafting process. The federal laws currently in force are compiled in a document known as the U.S. Code.
The President and the agencies they oversee enforce the laws of the United States. Sometimes this enforcement looks like stereotypical law enforcement (for example, FBI agents investigating someone who has broken a federal law). But often it involves agencies creating regulations that provide specific detailed guidance on how individuals and entities should follow laws.
The judicial branch interprets the meaning of laws, applies laws to individual cases, and decides if laws violate the Constitution.
The Ohio state government is closely modeled on the U.S. federal government. One key difference from the federal government is that is relatively easy to pass Ohio constitutional amendments via ballot measure, so in many cases very specific policies that in federal law would be described in the code are described in the Ohio constitution.
In general, state governments do a good job of describing themselves on the their websites, so basic internet searches can usually retrieve the needed websites. Always look for .gov search results. Useful searches include:
In the United States, the federal government has jurisdiction over most immigration matters. Most of the executive agencies that manage immigration are in the Department of Homeland Security, which includes U.S. Citizenship and Immigration Services, U.S. Immigration and Customs Enforcement, and U.S. Customs and Border Protection. The State Department also plays a role.
Due to some quirks in immigration law, many of the judges who oversee individual immigration cases are part of the Department of Justice, through the Executive Office for Immigration Review (so, not part of the judicial branch!) Other federal judges from the judicial branch, including the Supreme Court, also evaluate and interpret immigration laws.