There is no definitive answer to this question because it depends on the specific laws of the country or state in question. However, in most cases, using a forward grip on a rifle is not illegal.
A forward grip is simply a handle that is attached to the front of a firearm. This allows you to hold the gun with two hands and increases stability, which can be helpful for accuracy when shooting. A forward grip can also provide additional leverage for pushing or pulling the gun.
While many people see forward grips as advantageous, they can also be controversial because some people believe that they make guns too easy to shoot and pose a safety risk. For this reason, some states or countries may ban their use, but it is typically legal to use a forward grip on a rifle in the United States.
If you are unsure about the laws in your area, it is always best to consult with a local attorney or law enforcement officer.