Web search has become critical infrastructure, yet today it is dominated by a handful of proprietary, largely non-European platforms. OpenWebSearch.eu responds with the vision of a public, open and legally sustainable European Open Web Index (OWI) that supports digital sovereignty, pluralism and innovation. The LISA Whitepaper provides the legal framework for developing and operating the OWI through “compliance by design”: an applicable-law matrix, risk register, and operational policies across four clusters: 1) illegal content (DSA notice-and-action, no general monitoring, transparency), 2) privacy and data protection (GDPR minimisation, lawful basis, data subject rights), 3) ownership/IP (copyright & TDM exceptions, database rights), and 4) sharing/governance (tiered licences OWIL/OWICL/OWIDAA, takedown propagation, versioning, audits). It concludes with governance recommendations for a public-interest steward and federated operations to keep the index open, accountable and trustworthy.