Mining pools and 51% attacks

One question regarding mining pools that I have been wondering about. As far as I understand mining pools, they pool together the hashpower of a number of individual miners with the aim of increasing the likelihood of mining a block and receiving the block reward. Even though they have the ability to aggregate the hashing power of individual miners they themselves do not own the mining equipment; the latter is in the possession of the miners who have chosen to contribute their hash power to the respective mining pool. Does this mean that the entities administrating those mining pools cannot initiate a 51% attach on the Bitcoin network?