The Homeland Security Act, passed by Congress in 2002, created the Department of Homeland Security (DHS) to prevent, defend against, and help recover after terrorist attacks. Soon after the department's inception, its color-coded national terrorism threat advisory chart and revised airport security procedures became its most widely recognized policies. As of 2010, DHS listed its main areas of responsibility as: guarding against terrorism, securing U.S. borders, enforcing immigration laws, maturing and unifying the department, and improving disaster readiness, response and recovery.
The widely publicized DHS air travel restrictions fall under the jurisdiction of its Transportation Security Administration (TSA). According to TSA rules, most sharp items are prohibited in carry-on luggage. Exceptions apply to disposable razors and scissors with blades less than four inches long. Box cutters, ice picks, knives and other sharp items are allowed in checked baggage only. Most sporting goods, such as baseball bats and golf clubs are only allowed in checked baggage. Guns and firearms--including pellet guns and items that look like guns--are allowed only in checked baggage if they are unloaded and in cases. Flares and gunpowder are completely prohibited. Ammunition is allowed on some flights, but must be declared. Self-defense items are only allowed in checked baggage. Explosive items and flammable materials are prohibited on all flights.
The TSA requires carry-on liquids to meet the "3-1-1 rule:" liquids or gels must be in containers of three ounces or less; they must be placed in a one-quart, clear plastic bag; and only one bag is allowed per passenger. Containers with more than three ounces of liquid or gel should be put in checked luggage. Exceptions apply to medications, baby food and breast milk, which are allowed "in reasonable quantities" for flight times.
In addition to traveling restrictions, DHS issues a terrorist threat level advisory specifically for the airline sector. Threat levels are color-coded. Low-risk is identified with a green bar. "Guarded" level means there is a general risk and is marked with a blue bar. A yellow bar symbolizes "elevated" or significant risk of terrorist attack. High risk is illustrated with an orange bar and severe risk, the highest level, is marked with a red bar. The general terrorist threat advisory uses the same color-coding, but the airline sector is often at higher risk than other national sectors.
To help secure U.S. borders, DHS has implemented the Western Hemisphere Travel Initiative requiring all travelers entering or re-entering the U.S. to present a valid passport or equivalent. DHS has also instated the Real ID Act of 2005, which sets national standards for all state-issued driver's licenses and identification cards.