Restrictive vs. Non-restrictive Elements Answer 9
In the late twentieth century, Charlton Heston who became president of the National Rifle Association led the fight for toy manufacturers to produce more realistic-looking toy guns.

Answer:

In the late twentieth century, Charlton Heston, who became president of the National Rifle Association, led the fight for toy manufacturers to produce more realistic-looking toy guns.

Commentary:

Charlton Heston is already well-specified. There is only one Charlton Heston. The relative clause "who became president of the National Rifle Association" refers back to Charlton Heston, so it must be set off with commas.