Nodes enforce rules

Consensus rules are enforced by every full node independently: each node validates every block and transaction against its own copy of the rules and discards anything invalid, regardless of how much proof-of-work backs it. Miners choose transaction ordering and inclusion; nodes determine validity. A block paying an oversized subsidy or containing an invalid signature is simply not Bitcoin to the network's nodes, no matter who mined it.

Nuance: The practically decisive nodes are "economic" nodes — those operated by exchanges, merchants, custodians, and users who accept or reject coins. Hashrate follows the chain those nodes value, because blocks rejected by the economy earn nothing. This is the structural reason "miners control Bitcoin" claims fail (see miners-capabilities-limits).

Common misstatements:

• "Miners run the network; nodes just relay." — Nodes are the rule enforcers; mining without node acceptance produces worthless blocks.
• "More hashrate means more say over the rules." — Hashrate competes for ordering rights within the rules; it confers no authority to change them.
• "Running a node doesn't matter." — Verifying your own incoming payments against your own node is the trust-minimized mode of use; aggregate node policy is what makes rule changes require broad consent.