The Authentication and Authorization for ConstrainedEnvironments (ACE) framework provides fine-grainedaccess control in the Internet of Things, where devices areresource-constrained and with limited connectivity. The ACEframework defines separate profiles to specify how exactlyentities interact and what security and communication protocolsto use. This paper presents the novel ACE IPsec profile, whichspecifies how a client establishes a secure IPsec channel witha resource server, contextually using the ACE framework toenforce authorized access to remote resources. The profilemakes it possible to establish IPsec Security Associations, eitherthrough their direct provisioning or through the standardIKEv2 protocol. We provide the first Open Source implementationof the ACE IPsec profile for the Contiki OS and testit on the resource-constrained Zolertia Firefly platform. Ourexperimental performance evaluation confirms that the IPsecprofile and its operating modes are affordable and deployablealso on constrained IoT platforms.