Which of the following best describes an unenforceable restriction?

An unenforceable restriction typically refers to a provision that violates legal standards, such as discrimination laws. An example of this is a restriction that prohibits ownership by a certain race. Such a restriction is impermissible under laws like the Fair Housing Act, which has established that discrimination based on race, color, national origin, religion, sex, familial status, or disability is unlawful in housing practices. Therefore, this form of restriction cannot be enforced legally and is considered void.

In contrast, other options, such as limiting property use to specific individuals or requiring written agreements for alterations, may have enforceable elements in certain contexts, depending on how they are framed and the relevant laws. Mandating a specific property tax rate could also be subject to valid statutory or municipal authority. However, any restriction that infringes on fundamental rights – particularly those regarding equal treatment under the law – is inherently unenforceable, highlighting why the prohibition of ownership based on race is correctly identified as an unenforceable restriction.