Final answer:
Illegal aliens are not a constitutionally valid type of roadblock. General law enforcement and driver's license checks are examples of constitutionally valid roadblocks.
Step-by-step explanation:
Of the options listed, illegal aliens is not a constitutionally valid type of roadblock. Constitutionally valid roadblocks include general law enforcement roadblocks, which are set up by law enforcement agencies to stop and check vehicles for various reasons, such as checking for driving or illegal substances.
Another constitutionally valid roadblock is a driver's license check, which is typically conducted to ensure that drivers have a valid license. However, it is important to note that the constitutionality of roadblocks can vary depending on the specific circumstances and the laws of each jurisdiction.