Short answer, yes… but it really depends on what type of refrigerant you will be brining into the country. There are some types of Refrigerant that are monitored and only allowed a certain amount of imports per year. These types include R-12 and R-22 as well as any other CFC or HCFC classes.
If you are looking to bring in HFCs such as R-134a, R-404A, or R-410A there is not limit set today on what you can bring in. This may change in the future as HFCs are slowly being phased out in the United States. It is all voluntary at this point but that could change in the coming years.
Lastly, be sure that you trust your supplier from over seas. There has been counterfeit refrigerant on the market over the past few years. Not only are you getting ripped off but this counterfeit can be dangerous. Most of the time companies will try save money and short change the manufacturing process. This can lead to bad chemical compositions and even lead to extremely flammable product.