just to add to daas yochids explanation: There is an “old” machlokes between the Pri Chodosh and the Chsam Sofer regarding chalav akum (milk milked by a non jew without the supervison of a jew) in a situation where we know for sure that the milk is from a kosher species. the example given is if a goy milks milk and it is known that there are no non kosher animals in the city. the pri chodosh holds that the milk is permitted bec we know for certain that it is kosher, the chsam sofer disagrees and says that chazal decreed (gozer b’minyan) that chalav akum is assur therefore it is assur in all circumstances. R Moshe writes that EVEN ACCORDING TO THE CHSAM SOFER the milk produced in USA by a company that the milking is not being watched by a jew (what is commonly refered to as cholov stam) is still permitted. R Moshe goes into great detail explainig this but the crux is that since there is a fear of being caught by the government it is “Anan Sahady” (as if there are witnesses testifying) that the milk is from a kosher species therefore has the same status as cholov yisroel and is mutar. many other rabbonim question the extent of the fear that companies have and therefore disagree with R Moshe.
It is interesting to note that the Chazon Ish is very much ‘mashma’ that he paskens like the pri chodosh, and therefore it is possible that the chazon ish would also allow the drinking of what we call cholov stam.
on a side note there may be a didderent problem with cholov stam- they may be consired cholov TREIFAH, this issue was discussed previosly on the coffee room.