In order for discrimination to trigger the protection of federal law it must be directed against an individual on account of their skin color, race, gender, national origin, disability, age, sexual orientation, religion, or a limited number of other categories. Laws prohibiting discrimination based on race are strongest and have been on the books for the longest period of time. Other categories have been introduced more recently and may be expansive or restrictive depending on the category and context. A combination of legislation and Supreme Court interpretation of existing laws have led to an expansion of civil rights to include groups that were not previously protected. Transgender and homosexual victims were not, at one time, protected by anti-discrimination laws. In addition to extending protection to these individuals; legislative changes now also protect those perceived to belong to one of the enumerated groups by their persecutor. For example, if someone was denied a promotion at their job because they are believed to be homosexual they would now have an actionable claim of discrimination against their employer, even if they are actually heterosexual.