The main purpose of Federal Law Enforcement Agencies is to insure that the statutes and responsibilities granted to the Federal government by the Constitution are enforced and executed upon. In addition to investigating crime on a Federal level, the Federal government is responsible for regulating and enforcing Federal Laws relating to everything from US Customs to National Parks to the US Postal Service to Interstate Commerce.

Pros:

Generally better salaries and benefits
Access to resources of the Federal government
Agencies are generally more specialized

Cons:

Generally more bureaucratic, larger agencies
Travel Intensive in many cases
Less variety of work (fewer types of incidents)

To find out more about federal agencies, you can research many of them by clicking below:

Federal Bureau of Investigation
US Customs Service
Drug Enforcement Administration
US Secret Service
US Marshals Service
US Park Police
US Border Patrol
Bureau of Alcohol Tobacco and Firearms
Immigration and Naturalization Service
Postal Inspection Service
Fish & Wildlife
Internal Revenue Service Criminal Investigation Division